Rats

Rats are large rodents, and in the US two species cause nearly all home problems: the Norway rat (also called brown or sewer rat), which burrows and lives low, and the roof rat (black rat), which climbs and lives high. Both eat almost anything, need water every day, breed fast, and gnaw through wood, plastic and wiring, so a rat problem is a bigger deal than mice.

This page covers identification, diet, lifespan, behavior and health risks. For the action plan, see how to get rid of rats.

What rats look like

• Body: 6-10 inches, plus a tail of 6-8 inches; roof rats weigh 5-10 ounces, Norway rats 7-18 (adults average 12-16 ounces, per ICWDM).
• Fur: coarse, brown or gray (Norway) or black to gray-brown (roof).
• Head: blunt (Norway) or more pointed (roof) snout; ears smaller relative to head than a mouse's.
• Tail: thick and scaly.
• Teeth: orange-yellow incisors that grow about 5 inches a year, which is why rats gnaw constantly.

Full comparison: roof rats vs Norway rats. Unsure whether it's a rat at all? See mouse vs rat.

"Dumbo rats," "fancy rats" and the like are domesticated Norway rats kept as pets, and "river rats" is usually slang (or a name for muskrats or nutria). And "The Rats: A Witcher Tale" is a Netflix film, not a pest.

What do rats eat?

Rats are omnivores and eat whatever is abundant.

• Norway rats prefer grain, meat, fish, pet food and garbage. They forage in trash cans, compost, chicken coops and dumpsters.
• Roof rats prefer fruit, nuts, seeds, berries, snails and vegetables, so citrus and avocado trees, bird feeders and ivy-covered fences attract them.
• Both need water regularly, unlike house mice: pet bowls, leaky faucets and irrigation, pools, condensate lines.

Behavior

• Nocturnal, most active after dusk.
• Cautious of new things (neophobia). Rats avoid new objects and food for several days to weeks, roof rats more than Norway rats, which is why traps set right away often fail.
• Creatures of habit. They use the same runways along walls, fences and pipes, leaving dark greasy rub marks and packed trails in grass.
• Range 100-500 feet from the nest for Norway rats and 300 feet or more for roof rats (UC IPM), so food in your neighbor's yard can feed rats nesting in yours.
• Strong and athletic. Rats climb rough walls and pipes, swim (and can come up through toilet drains), and young rats squeeze under a door with a 1/2-inch gap.

Can rats climb walls?

Yes. Rats can climb brick, stucco, rough siding, trees, downspouts and wires, and run along fences and power lines. Roof rats are especially good climbers and get into attics from overhanging branches. Smooth surfaces like metal flashing or glass stop them.

Rat nests

Norway rats dig burrows 2-4 inches wide along foundations, under sidewalks and slabs, under woodpiles, sheds and shrubs, with an extra "bolt hole" for escape. Active burrows (2-3 inches across, per ICWDM) have smooth, packed entrances free of debris and cobwebs, often with rat hairs at the rim. Indoors they nest in basements, crawl spaces, behind walls and under floors.

Roof rats build nests of shredded insulation, paper and plant fibers in attics, wall voids, dense ivy, palm trees and stacked materials.

How long do rats live and how fast they breed

Wild rats usually live about one year; few survive longer than 18 months. Pet rats live 2-3 years. Females mature at 2-3 months, gestation is 21-23 days, and a litter is typically 6-12 pups. UC IPM puts Norway rats at 4-6 litters a year (a female weans 20 or more young a year) and roof rats at 3-5 litters of up to 8. Baby rats are born pink and blind and leave the nest at about 3-4 weeks. A pair moving into a shed in spring can become dozens by fall.

Are rats dangerous?

Rats are more of a health and property risk than mice.

• Disease. Rats can spread leptospirosis (through urine in water and soil), foodborne bacteria such as salmonella, E. coli and campylobacter, murine typhus, rat-bite fever, and fleas that carry other pathogens. Their urine and droppings contaminate food and surfaces.
• Bites. Rats bite when cornered or handled, and occasionally bite sleeping people, mainly infants, in heavily infested housing. Wash any bite with soap and water and see a doctor promptly: rat bites can cause infection and rat-bite fever.
• Property damage. Gnawed wires (a fire risk), water lines, plastic pipes, insulation, car wiring, irrigation lines and garden produce.
• Allergens and asthma in heavily infested homes.
• Not rabies. UC IPM notes commensal rats and mice do not carry rabies.

Don't sweep or vacuum droppings. CDC advises airing the area out for 30 minutes, wearing gloves, and soaking droppings and urine spots with a fresh mix of 1.5 cups bleach per gallon of water (about 1:9) or an EPA-registered disinfectant for 5 minutes, then wipe up with paper towels. See a doctor if you develop fever, headache, muscle aches or red eyes after contact with rat urine or water in flooded areas.

Rats in the house: how they get in

• Gaps around pipes, utility lines and AC lines
• Foundation cracks, crawl space vents, gaps under garage doors
• Burrows under slabs that open into wall voids
• Roof rats: tree branches and utility lines to the roof, then gaps at eaves, vents and roof joints
• Sewer lines and broken drain pipes (Norway rats)

What people who've had rats say

On r/pestcontrol the same lessons repeat. Rats are usually heard before they're seen: scratching and thumping in the ceiling at night is the most common first sign, and arguments about whether it's rats, squirrels or bats are settled fastest with a trail camera. People who relied on monthly bait visits often still had rats months later; technicians say sealing entry points is most of the job. Roof-rat owners in the South and California report rats chewing PEX water lines and wiring in attics, and many who put poison in the attic regretted it when rats died in the walls and the smell lasted weeks. Quotes for attic rats range from about $1,000 to $7,000, with the largest usually including insulation replacement, which many veteran pros consider unnecessary unless it's heavily soiled.

What to do about rats

The approach in short (details in how to get rid of rats):

1. Remove food, water and shelter: lidded trash bins, no pet food outdoors, pick up fallen fruit, move woodpiles, trim vegetation off the house.
2. Trap with pre-baiting: rat-size snap traps along runways, left unset with bait for a few days, then set all at once.
3. Exclude with hardware cloth, sheet metal, concrete and steel wool plus sealant.
4. Bait stations with rodenticide only in tamper-resistant stations, mainly outdoors and with care for pets and wildlife.

When to call a pro

Call a pest control company if rats are inside the living space, you hear them in walls or the attic, you see them in daytime, or a month of trapping and cleanup hasn't stopped them. In apartments, contact your landlord or building management; rats are a building problem. Expect roughly $300-$700 for initial rat removal and more for full exclusion (approximate). See rodent control.